Decrease of soil fertility and release of mercury following deforestation in the Andean Amazon, Napo River Valley, Ecuador.

Soil erosion and degradation provoked by deforestation in the Amazon is a global concern, and recent studies propose a link between deforestation, soil erosion and the leaching of naturally occurring mercury (Hg). In the Ecuadorian Amazon, elevated deforestation rates and the proximity of volcanoes could play an important role in soil fertility and soil Hg levels. The goal of this study is to evaluate the impacts of deforestation on Andisol and Inceptisol fertility and Hg levels in the Napo River Valley, Ecuador. Results show a significant decrease in surface soil organic matter (-15% to -70% of C and N) and exchangeable cations (-25% to -60%) in deforested plots. Hg concentrations at the surface (0-5 cm), higher in Andisols (225 ng/g average) than in Inceptisols (95 ng/g average), show a decrease of up to 60% following deforestation. Soil erosion exposes the mineral horizon, a layer with a higher Hg burden, to the elements thus provoking and accelerating Hg leaching. These results suggest that deforestation and the associated Hg leaching could contribute to the fish Hg contamination measured in the Napo River watershed.

Effects of manganese exposure on visuoperception and visual memory in schoolchildren.

BACKGROUND: Manganese (Mn) is an essential metal involved in multiple physiological functions. Environmental exposure to airborne Mn is associated with neurocognitive deficits in humans. Children, whose nervous system is in development, are particularly susceptible to Mn neurotoxicity. OBJECTIVE: The objective of this study was to assess the association between Mn environmental exposure, and effects on visuoperception and visual memory in schoolchildren. METHODS: We assessed schoolchildren between 7 and 11 years old, with similar socioeconomic status, from the mining district of Molango (n=148) and Agua Blanca (n=119, non-mining area) in Hidalgo state, Mexico. The Rey-Osterrieth Complex Figure (ROCF) test was used to assess visuoperception and short-term visual memory. Hair manganese (MnH) concentrations were determined. Linear regression models were constructed to estimate the associations between MnH and ROCF scores, adjusted for potential confounders. RESULTS: The geometric mean MnH was nine times higher in schoolchildren from the Mn mining area (5.25µg/g) than in schoolchildren from the non-mining area (0.55µg/g). For the ROCF Copy trial, MnH was significantly associated with an increase in distortion errors (tangency, closure), angle errors, overtracing (partial overtracing). In the Immediate Recall trial, MnH was significantly associated with increased overtracing (partial overtracing) and omissions, and negatively associated with the number of perceptual drawn units, total score and percentage immediate recall. CONCLUSIONS: MnH is associated with alterations in visuoperception and short-term visual memory in schoolchildren exposed to airborne Mn.

Very low level environmental exposure to lead and prolactin levels during pregnancy.

Lead (Pb) is a well-known poison interfering with calcium homeostasis and dopaminergic pathway. We hypothesized that environmental Pb exposure can interact with prolactin (PRL) secretion, regulated by calcium and dopamine, during pregnancy and in fetus. The objective of this longitudinal study was to determine the relationships between blood Pb concentration and serum PRL levels in 101 pregnant women recruited during pregnancy and their fetuses exposed to low environmental levels of Pb. We observed a significant negative relationship between maternal blood Pb concentrations and maternal serum PRL levels. Cord blood PRL was weakly correlated with blood Pb levels. Our results suggest that maternal physiological parameters in pregnancy can be modulated by low level of Pb exposure and indicate a particular susceptibility of pregnant women to its toxic effects.

Chromal focus of acquired chromatic discrimination loss and solvent exposure among printshop workers.

Acquired dyschromatopsia has been associated with exposure to organic solvents. However, the chromal focus of the loss may be indicative of its gravity. According to Kollner's rule, blue-yellow loss reflects changes in external retinal layers, while red-green loss appears to be indicative of internal retinal or optic nerve damage. The objective of the present study was to examine chromatic discrimination capacity of 30 printshop workers exposed to organic solvent mixtures, and of a non-exposed reference group. Colour vision was assessed with a colour arrangement test designed to detect acquired dyschromatopsia, the Lanthony D-15 desaturated panel. Quantitative analysis, using Bowman's colour confusion index, revealed significantly higher scores indicative of colour vision loss among the exposed workers as compared to the non-exposed. Analysis of covariance, with age as co-variate, showed colour confusion index to be significantly associated with job category. Similarly, qualitative analysis showed that the exposed workers presented a significantly higher prevalence of acquired dyschromatopsia as compared to the non-exposed group. However, analysis of the type of chromatic discrimination loss showed that among the nonexposed persons, dyschromatopsia was localized only in the blue-yellow range, while for 35% of the dyschromatopic-exposed persons, red-green loss as well as blue-yellow loss were present. Three-dimensional chi 2-analysis showed that the complex pattern of dyschromatopsia was not related to age, but to job category. These findings suggest that the type of dyschromatopsia, reflecting the gravity of neural alterations, may be a function of exposure level and/or the ophthalmotoxic properties of the particular solvents used.

Olfactory threshold shift following controlled 7-hour exposure to toluene and/or xylene.

The present study was undertaken to examine olfactory perception threshold (OPT) shift following exposure of healthy subjects to toluene and/or xylene in an inhalation chamber. Five volunteers were exposed to 50 ppm toluene, 40 ppm xylene or an additive mixture of the two, for a period of 7 consecutive hr in an inhalation chamber. A Latin square design was used and subjects were exposed over 3 consecutive days/week, with an 11-day interval between each 3-day session. Olfactory perception thresholds, measured in decismels (ds), were ascertained for both toluene and PM-carbinol, contained in 100 ml bottles with serially increasing concentrations (Olfacto-Lab Kits # 191 & 11). Test administration was based on the forced choice method. Analysis of variance of pre-exposure OPTs indicated that for both toluene and PM-carbinol, significant differences were observed between individuals (p less than 0.05), but not between days or weeks. Measurements, made immediately following exposures revealed a significant six-fold increase in OPT for toluene (median: 15 ds), while PM-carbinol OPT remained stable. Individual differences were observed, but there was no effect of type of exposure, day, week, or interactions. OPT for toluene, determined at intervals following cessation of exposure, indicated a return to pre-exposure values at a mean rate of 6.8 ds/hr. The findings of this study suggest that there is a substantial olfactory threshold shift during a 7-hr period, specific to a particular solvent or family of solvents. Receptor-specific saturation is proposed as the underlying mechanism.

Olfactory adaptation, threshold shift and recovery at low levels of exposure to methyl isobutyl ketone (MIBK).

The anatomic position of olfactory receptors renders them vulnerable to airborne pollutants. Chamber inhalation studies have shown dose-dependent olfactory adaptation and temporary olfactory threshold perception shift for particular inhaled substances. The present study was undertaken to examine olfactory perception threshold (OPT) and adaptation of healthy subjects exposed for 7h to MIBK. Volunteers (n = 4) were exposed in an inhalation chamber to MIBK at concentrations of 20 ppm and 40 ppm. For each of 6 exposure days, OPT for MIBK and PM-Carbinol were determined once before exposure and at 3 successive intervals following exit. Exhaled air samples were taken at regular intervals during and after exposure. Perceived odor intensity and symptoms were ascertained through a questionnaire filled out hourly. On all days, post-exposure OPT-MIBK at chamber exit was significantly higher than pre-exposure, representing a ninefold increase in concentration; recovery was dose-dependent and not complete 95 min. after exit. No threshold shift was observed for OPT-PM-Carbinol. Perceived odor intensity was high when entering the chamber, but diminished with time, stabilizing after approximately 2 hours. Symptoms of nose, eye or throat irritation and headache were present in some subjects. The findings of this study suggest that at these levels of MIBK, there is olfactory adaptation during exposure and a transient OPT shift for the inhaled substance. Persons exposed professionally or environmentally to certain organic solvents may suffer temporary smell loss which hinders odor detection.

Neuropsychological impairment among former microelectronics workers.

Although chemicals posing potential neurotoxic hazards are commonly used in the microelectronics industry, there has been no systematic study of possible chronic nervous system effects in microelectronics workers. The objective of the present study was to assess neuropsychological functions of a group of former microelectronics plant assembly workers and a group of referents, using a matched pair design. During employment, the former microelectronics workers had been exposed to multiple organic solvents, including trichloroethylene, xylene, chlorofluorocarbons and trichloroethane. Referents were recruited from the same geographic region. From a pool of 180 former workers and 157 referents, 67 pairs were matched on the basis of age, sex, ethnicity, educational level, sex and number of children. Comparison of results on the subtests of the California Neuropsychological Screening Battery-Revised (CNS-R) revealed significantly lower performance by the former microelectronics workers on tests of attention/concentration, verbal ability, memory functions, visuospatial functions, visuomotor speed, cognitive flexibility, psychomotor speed, and reaction time (t-test for pairs or Wilcoxon Signed Rank p less than 0.05). No significant differences were observed for performance on tests assessing mental status, visual recall, tactile function and learning. This overall pattern of impairment is consistent with organic solvent-related chronic toxic encephalopathy, and possible early stages of dementia. These findings underline the need for more studies among workers currently or previously employed in microelectronics industries.

Aftermath of a chemical spill: psychological and physiological sequelae.

Psychological, and psychophysiological sequelae were studied in a community which had experienced a railroad chemical spill of 19,000 gallons of the toxic pesticide metam sodium. Information was collected on 350 persons living in the area of the spill (spill residents) and 114 nonexposed controls, recruited using a randomized sampling strategy, from a nearby similar, but unexposed control town. Psychological measures used were the MMPI-2, POMS, IES Scale, Environmental Worry, Perceived Social Support and Perceived Control Scale. Physiological measurements were two measurements of blood pressure, pulse, and salivary cortisol level, taken both at the beginning and the conclusion of the study. Demographic and medical information was asked in a Questionnaire. Results indicate greater levels of depression, anxiety, and somatic symptoms in the spill residents in addition to greater environmental worry and lower perceived social support. Spill odor perception was related to increased psychological and physiological sequelae. The spill residents had higher blood pressure and less fluctuation of cortisol levels than the controls. Comparison of spill residents who were litigants and those who were not, indicates no differences for blood pressure, pulse, and cortisol, MMPI-2, Environmental Worry and the Control Scale. Litigants scored slightly higher on the IES, Intrusion and the POMS scales. No dose/response relationship between distance to the river and evacuation status was obtained. The chemical spills was associated with a wide variety of psychological and physiological reactions.

Quantification of neuromotor function for detection of the effects of manganese.

The effect of low level exposure to manganese (Mn) was examined in 297 subjects from southwest Quebec. Blood manganese (MnB) levels as well as other possibly relevant variables were obtained. We tested equipment and analysis procedures that we have developed to quantify aspects of motor function thought to be affected by exposure to toxins, in particular, rapid alternating movements, rapid and precise pointing movements, and tremor. (1) The eurythmokinesimeter measures timing and precision of contacts between a hand-held stylus and a pair of metal targets (proximal/distal). This roughly approximates the finger-to-nose test of the UPDRS. Characteristics quantifying speed, precision and regularity of the movements were calculated, as well as multiple contacts due to tremor and an index based on Fitts' Law eliminating the effect of the trade-off between speed and precision. (2) The diadochokinesimeter accurately measures rapid rotation of the forearms (pronation/supination). Characteristics quantifying the range, speed, period, shape and regularity of the oscillatory movements were calculated, as well as the smoothness of the movement on a fine scale and the coordination between the two hands. (3) Postural tremor of the arm and hand was measured using the accelerometry-based "TREMOR" system of Danish Product Development. We used the amplitude and frequency characteristics provided by the TREMOR system: intensity, center frequency, dispersion and harmonic index. Previous studies have shown that these tests are sufficiently sensitive to detect small differences in performance of different groups of subjects, with indications that some characteristics are also specific to particular conditions. In this study, significant though small effects related to age and gender were found in many of the characteristics. When effects of other variables are removed, low-level exposure to Mn was found to be associated with a decrease in ability to perform regular, rapid and precise pointing movements, a decrease in ability to attain high maximum rotation speeds in rapid alternating movements, and an increase in regularity of tremor oscillations. Moreover, the effects are age-related for levels of MnB 7.5, micrograms/L.

Color vision loss among styrene-exposed workers neurotoxicological threshold assessment.

Styrene represents nowadays one of the most used organic solvent. The current exposure limit proposed for this chemical differs significantly from country to country: the Threshold Limit Value-Time Weighted Average (TLV-TWA) proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) is 50 ppm while the German, Finnish and Swedish occupational exposure limit is 20 ppm. Nevertheless, effects on the nervous system were recently reported in workers exposed at TWA styrene levels below the current TLV. Neuro-optic pathways have been shown to be particularly vulnerable to organic solvent exposure. Analysis and measurements of visual functions can provide important information on early neurotoxic effects. Previous studies support the hypothesis that styrene exposure can induce a dose-dependent color vision loss. The aim of this study is to assess a threshold level below which no detectable effect occurs for color vision. We applied a sub-application of the change point problem in two-phase regression considering one phase as a constant line. In accordance with this model the maximum-likelihood technique was used as a method to examine the dose- effect relationship between external styrene exposure and chromatic discrimination. The present article presents a joint analysis of data from two previously published studies, one carried out in Canada and the other in Italy. The age and seniority of the workers from both countries were remarkably similar, as were the process type, the chemicals used and the work-tasks of exposed subjects. The mathematical method presented here shows the existence of a statistically significant threshold. This finding shows that, in fiberglass-reinforced plastics industry, visual color impairment could be significantly detected above 4 ppm (upper limit of the confidence interval at 5% = 26 ppm). The exact clinical meaning of this effect, and also the progress of the impairment in exposed workers, is still to be assessed in further studies. The results of our study support the need of a reduction of the occupational limits for styrene in workplaces to values close to or lower than German, Finnish or Swedish exposure limits.

Pilot study of peripheral markers of catecholaminergic systems among workers occupationally exposed to toluene.

In a pilot study, serum dopamine beta-hydroxylase (DBH), platelets monoamine oxidase type B (MAO B) activities and basal plasma prolactin (PRL) were measured, among 10 workers occupationally exposed to toluene and 10 control subjects, preceding and immediately following vacation. Six exposed subjects were employed in an adhesive tape making industry and 4 in a paint making industry. Their median basal levels of urinary hippuric acid were 0.44 mmole/mmole creatinine (cr) (range 0.23-1.97) and 0.18 mmole/mmole cr (range 0.15-0.19) respectively, the second to last morning of the work week, preceding vacation. The level of basal urinary hippuric acid among the control group was 0.26 mmole/mmole cr (range 0.03-0.38). The workers from the adhesive tape plant reported a significantly higher number of symptoms experienced frequently (Kruskal, Wallis, p < 0.05). On a group basis, serum DBH was lowest among the workers from the adhesive tape plant, who had the highest levels of basal urinary hippuric acid. In addition, a negative relation was observed between hippuric acid and serum DBH, preceding and following vacation (Rho = -0.46, p = 0.05; Rho = -0.51, p = 0.03). The observed changes in serum DBH activity are consistent with its decrease in human, following long-term exposure to styrene, another aromatic hydrocarbon. The findings of this pilot study, on a limited number of individuals suggest that DBH may be a sensitive peripheral bioindicator. Further studies of larger groups should be done to confirm the decrease in serum DBH activity with toluene exposure and explore whether this alteration is related to the neurotoxic impairments associated with exposure.

Symptom base rates after chemical exposure for white, Hispanic and African-Americans.

The results of a symptom checklist of three matched-pair studies (N = 460) of the following exposed groups are presented: Study 1, a primarily white community (N = 220) environmentally exposed to the pesticide metam sodium; Study 2, a Hispanic group (N = 180) who worked in a microelectronics plant and had extensive past exposure (M = 6.7 yrs) to multiple organic hydrocarbon solvents; and Study 3, an African-American group (N = 168) environmentally exposed to sulfuric acid. Each exposed group was compared to a matched (race, age +/- 3 years, gender, education +/- 2 years and number of children) unexposed reference group, resulting in 90 pairs for the white metam sodium group, 62 pairs for the Hispanic organic solvent group, and 78 pairs for the African-American sulfuric acid group. Symptom prevalence rates and relative risk ratios show very strong associations: in Study 1, the relative risk for all 33 symptoms ranged from 1.5 to 37; in Study 2, the relative risk for 31 of the symptoms ranged from 1.5 to 11.1; and in Study 3, the relative risk for 16 of the symptoms ranged from 1.5 to 6. Mann Whitney U results of each symptom indicate significantly greater symptomatology in the exposed vs. the reference groups in all three studies: in Study 1, at p < .01 for all 33 symptoms; in Study 2, at p < .01 for 31 symptoms, and p < .05 for one additional symptom; and in Study 3, at p < .01 for 24 symptoms and p < .05 for another three symptoms. These results suggest a robust symptom complex following chemical exposure regardless of specific chemical.

Surveillance of early neurotoxic dysfunction.

Surveillance of early neurotoxic alterations was undertaken in 3 reinforced plastics plants, with a view to preventive intervention. Using a longitudinal study design, exposure parameters (environmental styrene in the respiratory zone of each worker and end-shift mandelic acid (MA)) and neurobehavioral performance (Neurobehavioral Core Test Battery and Field Assessment: Sensory Tests), were assessed at time zero (T0); recommendations were made to reduce exposure at jobsites with the highest risk. Reassessment was made two years later (T2). Complete exposure data was available for 118 workers at T0; 75 were still employed at T2; of these, 57 (76%) returned for testing. Those who returned had more seniority (p < 0.001) and higher MA (p < 0.01) and styrene (p < 0.05) levels at T0 than the others. Analyses, performed on the T0-T2 differences, showed improvement in exposure parameters in Plant 3, where lower levels were observed at T2 for styrene (p < 0.05) and MA (p < 0.001). workers in Plant 3 (n = 29) performed better (p < 0.05) at T2 for short term memory, perceptuo-motor speed, motor precision and manual dexterity; they reported more vigor (p < 0.05) and less anger (p = 0.07). This was not the case for the workers from the other plants. Generally, the T0-T2 difference in MA was associated (Spearman's Rho) with differences in color vision (p < 0.001), simple reaction time (mean and standard deviation), digit span forward, tension, fatigue and the number of symptoms (p < 0.05); aiming precision showed a similar tendency (p < 0.10). These findings suggest that group surveillance of early nervous system changes for jobs with exposure to neurotoxins, using a sensitive neurofunctional test battery, may be useful for preventive intervention.

Bioindicator and exposure data for a population based study of manganese.

Exposure data and bioindicators were obtained for a study whose objective was detection of early manifestations of manganese (Mn) neurotoxicity in a population with potential environmental exposure. The study included persons with no history of neurotoxic workplace exposure in Southwest Quebec, drawn from seven postal code regions, defining a set of geographically contiguous zones. Blood samples were analyzed for total Mn (MnB), lead (PbB), total mercury (HgT) and serum iron (FeS). Drinking water samples from participants' residences were analyzed for manganese (MnW). At 4 sites, limited 24-hour high volume air samples for total particulates (TP) and PM10, were analyzed for Mn and Pb. Sociodemographic and dietary information was obtained by self-administered questionnaire. The geometric mean (GM) for MnB values (n = 297) was 7.14 micrograms/L. Levels of MnB in women (n = 156; GM 7.50 micrograms/L) were significantly higher than in men (n = 141; GM 6.75 micrograms/L). No relationship was found between MnB and PbB or HgT. FeS was significantly higher in men (GM 18.38 mumol/L) than women (GM 15.0 mumol/L). For women, MnB was correlated to FeS, with a tendency to decrease with increasing age. For men, no relationship was found between MnB levels and either FeS or age, although FeS showed a strong inverse relationship with age. The 24-hour mean levels of MnTP at the 4 sites varied between 0.009 microgram/m3 and 0.035 microgram/m3; intersite differences were not significant. For Mn in PM10 (MnPM10), mean values ranged from 0.007 microgram/m3 to 0.019 microgram/m3; intersite differences were significant. A total of 278 MnW samples were obtained, 16 from residences served by wells. The GM for MnW was 4.11 micrograms/L (range: 0.50-71.1 micrograms/L, excluding wells; MnW for wells ranged from non-detectable to 158.9 micrograms/L. Individually, there was no relation between MnW and MnB. Geographic analysis of the MnB and MnW data by an algorithm grouping contiguous postal code zones, combined with air data, lead to definition of a geographic parameter, distinguishing two regions relative to a former manganese alloy plant, which contributed significantly to MnB. A multiple regression model was developed, explaining 6.7% of the variability in MnB (F = 5.12; p < 0.001); when controlling for gender, geographic region with higher levels of airborne manganese and the frequency of consumption of cereals and leaf vegetables contributed positively to MnB levels, while serum iron was negatively related.

Neuropsychiatric effects of manganese on mood.

Adverse mood effects of overexposure to Manganese (Mn) have been described in 15 studies which frequently report an association of Mn exposure with adverse effects in six dimensions of mood: 1) anxiety, nervousness, irritability; 2) psychotic experiences; 3) emotional disturbance; 4) fatigue, lack of vigor, sleep disturbance; 5) impulsive/compulsive behavior; 6) aggression hostility. Only 1:15 studies used a standardized psychological measure of mood, while the current study of environmental Mn exposure used two standardized mood scales in evaluating low levels of Mn exposure and mood sequelae. The Profile of Moods State (POMS) and Brief Symptom Inventory (BSI) were used, and results indicate that men who are older and have higher Mn levels show significant disturbances on four of the six mood dimensions. Increased scores were seen in the anxiety, nervousness, irritability; emotional disturbance; and aggression, hostility dimensions relative to those who had lower levels of Mn. The BSI and POMS are useful adjuncts in the assessment of mood/Mn effects.

Preliminary evidence of neurotoxicity associated with eating fish from the Upper St. Lawrence River Lakes.

Pollution of hydrographic basins has affected the flora and fauna that thrive in these aquatic ecosystems, and fish, which constitute an important food resource, often contain a plethora of potentially toxic chemicals. In a major research project on early neurotoxic effects of environmental exposure to manganese among residents in Southwest Quebec, fish consumption from 2 lakes of the Upper St. Lawrence River System, was surveyed as a potential confounding factor. Participants were selected using a random, stratified sampling strategy from lists of the Quebec Health Plan. Following exclusions, 273 men and women between 20-69 years were retained for the present analysis. A total of 103 (37.7%) reported eating fish from the Upper St. Lawrence. Although fisheaters and non-fisheaters were similar for most socio-demographic variables, significantly more fisheaters (65.2%) reported consuming alcoholic beverages as compared to non-fisheaters (42.4%) (Chi Sq. <0.01). To eliminate this possible bias, fisheaters were matched to non-fisheaters for the variables sex, alcohol consumption (never or occasionally vs. regularly), age (+/-5y) and education (+/-2y). A total of 63 matched pairs were thus created. Paired analyses (t-test or Signed Rank) showed that fisheaters had higher levels of blood organic mercury and lead. Analysis of nervous system functions revealed that both groups performed similarly on tests of sensory function, visual memory and recognition, fine motor performance and some motor tests, but fisheaters performed significantly more poorly (p<0.05) on tests requiring cognitive flexibility, word naming, auditory recall, and more complex motor tasks. The profile of deficits is consistent with diminished capacity for information processing. These observations were made within a study that was not specifically designed to examine the effects of fish eating from these two lakes, and the characterization of fish dietary habits has many limitations. Nevertheless, the findings are sufficiently compelling to warrant further studies, since fish from the Upper St. Lawrence Lakes are known to contain multiple neurotoxic substances.

Evidence of early nervous system dysfunction in Amazonian populations exposed to low-levels of methylmercury.

There is increasing concern about the potential neurotoxic effects of exposure to methylmercury in Amazonian populations due to mercury (Hg) release from gold-mining activities. A preliminary study was undertaken in two villages on the Tapajos River, an effluent of the Amazon, situated over 200 km downstream from the extraction areas. The study population included 29 young adults (< or = 35 years), 14 women and 15 men, randomly chosen from a previous survey. Hair analyses were conducted with cold vapor atomic fluorescence spectrophotometry. Total hair Hg (THg) varied between 5.6 micrograms/g and 38.4 micrograms/gl, with MeHg levels from 72.2% to 93.3% of the THg. A quantitative behavioural neurophysiological test battery, designed for use under standard conditions, in an area without electricity and for persons with minimal education was administered to all participants. The results of visual testing showed that although all participants had good near and far visual acuity, color discrimination capacity (Lanthony D-15 desaturated panel) decreased with increasing THg (F = 4.1; p = 0.05); near visual contrast sensitivity profiles (Vistech 6000) and peripheral visual field profiles (Goldman Perimetry with Targets I and V) were reduced for those with the highest levels of THg. For the women, manual dexterity (Santa Ana, Helsinki version) decreased with increasing THg (F = 16.7; p < 0.01); this was not the case for the men. Although the women showed a tendency towards reduced grip strength, muscular fatigue did not vary with THg for either sex. The findings of this study demonstrate that it is possible, using a sensitive test battery, to detect alterations in nervous system functions, consistent with knowledge on Hg toxicity, at levels below the currently recognized threshold of 50 micrograms/g THg.

Diadochokinesimetry: a study of patients with Parkinson's disease and manganese exposed workers.

Diadochokinesia, the ability to perform rapid alternating movements is often impaired in patients with extrapyramidal disease. It is a common sign among patients with Parkinsonism or manganism. In the present study we compare patients with Parkinson's disease (n = 11), workers formerly exposed to manganese (n = 10) and control subjects (n = 11) performing rapid alternating hand movements for 5 s under four conditions repeated twice (natural cadence and maximal speed with one or two hands). Data recorded using a diadochokinesimeter built in our laboratory and connected to a 486/33 microcomputer were digitized in real time while subjects rotated back and forth hand held foam spheres connected to flexible rods articulated with optical encoders. Significant differences were found between control subjects and patients with Parkinson's disease, but not with manganese exposed workers, in most variables examined. However, trajectory length (a combination of movement amplitude and velocity) indicated that manganese exposed workers and patients with Parkinson's disease were significantly different from the controls in functional asymmetries between right and left hand. In addition, workers and patients tend to have marked differences between the performance of right and left hands. Improved quantitative measurement of rapid alternating movements may prove to be an important tool in early and differential diagnosis of Parkinson's disease and manganese exposure.

Long-term exposure to "low levels" of manganese oxides and neurofunctional changes in ferroalloy workers.

Occupational exposure to manganese can cause early neurobehavioral effects in low- or a-symptomatic workers. A battery of neuropsychological tests was administered to a group of 61 ferroalloy male workers and 87 controls. The average (geometric mean) manganese concentrations in total dust at the plant have changed from 1981 to 1997 respectively from 1597.03 micrograms/m3 to 239 micrograms/m3 at the furnace area; from 151.53 to 255.76 micrograms/m3 at the casting area; from 167 to 54.7 micrograms/m3 at the maintenance (welding operations), yielding a current overall value of 54.25 micrograms/m3. A cumulative exposure index was calculated for each alloy worker and the average value (geometric mean) resulted to be 1204.87 micrograms/m3 x years, which divided by the average length of exposure (15.17 years), showed the concentration of 70.83 micrograms/m3 of manganese in total dust. Blood and urinary manganese geometric means resulted significantly higher in the exposed workers (9.18 micrograms/l and 1.53 micrograms/g creatinine, respectively) than in controls (5.74 micrograms/l and 0.40 microgram/g creatinine, respectively). A positive correlation was observed between the airborne manganese concentrations in total dust and blood manganese (n = 55; R = 0.36; R2 = 0.13; p = 0.0068), whereas no association resulted between cumulative exposure index and both blood manganese and urinary manganese. Higher prevalence of symptoms reporting was observed in the alloy workers concerning irritability, loss of equilibrium and rigidity. Tremor parameters including the central frequency and its dispersion, resulted to be statistically different in the exposed workers compared to the controls. Motor functions exploring the coordination of rapid and alternating movements and memory functions resulted to be impaired in the manganese workers. Dose-effect relationships were observed between the cumulative exposure index and some of the test results, whereas no relationship was found with the airborne manganese concentrations and the biological indicators of exposure. These findings are consistent with the existing knowledge of a cumulative mechanism of action of manganese, which must be carefully considered when setting safe exposure levels. In order to be protective for the entire working life, the average annual exposure level should be lower than 100 micrograms/m3.

Manganese neurotoxicity, a continuum of dysfunction: results from a community based study.

Excessive manganese (Mn) has been associated with neurobehavioral deficits and neurological and/or neuropsychiatric illness, but the level at which this metal can cause adverse neurotoxic effects, particularly with long-term exposure, is still unknown. The objective of the present study was to assess nervous system functions in residents exposed to manganese from a variety of environmental sources. A random stratified sampling procedure was used to select participants; persons with a history of workplace exposure to Mn and other neurotoxic substances were excluded. A self-administered questionnaire provided data on socio-demographic variables. Blood samples were analyzed for total manganese (MnB), lead, mercury and serum iron. Nervous system assessment included computer and hand-administered neurobehavioral tests, computerized neuromotor tests, sensory evaluation and a neurological examination. The present analyses include 273 persons (151 women and 122 men); MnB range: 2.5 micrograms/L-15.9 micrograms/L (median: 7.3 micrograms/L). Multivariate analyses were used and neuro-outcomes were examined with respect to MnB, taking into account potential confounders and covariables. Results were grouped according to neurofunctional areas and MANOVA analyses revealed that higher MnB (7.5 micrograms/L) was significantly associated with changes in coordinated upper limb movements (Wilks' lambda = 0.92; p = 0.04) and poorer learning and recall (men: Wilks' lambda = 0.77; p = 0.002; women: Wilks' lambda = 0.86; p = 0.04). Further analyses revealed that with increasing log MnB (Simple regression: p < 0.05) performance on a pointing task was poorer, frequency dispersion of hand-arm tremor decreased, while harmonic index increased, and the velocity of a pronation/supination arm movement was slower. An Mn-age interaction was observed for certain motor tasks, with the poorest performance observed among those _50 y and in the higher MnB category. Differences between genders suggest that men may be at greater risk than women, although effects were also observed in women. These findings are consistent with the hypothesis that Mn neurotoxicity can be viewed on a continuum of dysfunction, with early, subtle changes at lower exposure levels.